APPLICANT'S ABSTRACT: The 21st century is likely to begin in the midst of a major heroin epidemic in New York City. An emergent cohort of users may switch between injecting, intranasal use and smoking the drug, with corresponding risks of disease, crime, violence and other forms of personal familial and communal dysfunction. Depending on how they are organized, distributors will variably affect the quality of life in many neighborhoods. The risk of HIV/AIDS will be a concern in New York, where 50% of IDUs are HIV+ while only 15% receive treatment. Four hundred (400) individuals representing the ethnic, age and gender composition of the city's evolving population of users and distributors will participate in this study to monitor heroin ethnographically to the year 2000 in New York City. They will manifest a range of use patterns and distributing styles. Five ethnographers, aided by four part-time assistants, will select them in a sampling of the city's heroin-affected neighborhoods. They will employ research techniques such as participant observation, the use of key informants, several interview formats, discussion groups and various measurements. They will continuously issue updates, presentations and publishable papers for the benefit of academics, policymakers and service providers. The specific aims of this applications will be to: 1) establish an ethnographic monitoring network to track the developmental cycle of heroin use in New York City from 1995 to 2000; 2) describe the structure and functioning of existing and emergent heroin distribution, specifying changes in the modus operandi of distributors, prices, purity, unit quantities and measuring the impact of law enforcement and public responses; 3) document transformations over time in beliefs, norms, and practices of each category of users towards heroin use/sales, other drugs, sex work, HIV/AIDS risk behaviors, other social ties, non-drug criminality, violence, maintenance/loss/regaining of control, relationships with law enforcement and drug misuse treatment.